1What light does on its way to the wall
Light flies as rays — and they can aim the same way or spray apart
You only need two ideas. Watch each one:
Light travels as rays
A ray is a little arrow of light heading in a direction. Where the arrows land is where you see a bright spot. Where they don't reach stays dark.
Same way & in step, or scrambled
Rays can march the same way and rise and fall together — like one marching band. Or they can spray every which way at once, like a jumbled crowd.
2Two ways to throw light
The marching-band beam vs the spray-everywhere bulb
A laser and a flashlight don't send out their light the same way at all:
The marching-band beam
Every ray heads the same direction and in step — they leave as one tight, straight beam.
The spray-everywhere bulb
The bulb throws rays out in every direction at once — they fan out as soon as they leave.
3Your turn — open and close the spray
Aim one light at the wall and squeeze its rays together
Here's one light shining at a wall. Drag the slider to close up the spray until the rays all head the same way — watch the wide blob pull in to a tight dot. Wide spray = blob. Narrow spray = beam.
4Now slide the wall across the room
Can a weaker beam make a brighter spot?
A new comparison: this flashlight sends out four times as much light as the laser. Their spread angles stay fixed. Predict which will deliver more light to each small patch of the distant wall.
Guess before you slide the wall
The flashlight has 4 light-power units and the laser has 1. At the far end of this model room, which spot will be brighter per equal area?